Tire rubber composition

Abstract

A rubber tire composition, comprising: from 20 to 150 parts by weight of carbon black incorporated in 100 parts by weight of rubber; at least 30 parts by weight of said rubber being a star type solution polymerized random styrene-butadiene copolymer rubber comprising 10% to 20% by weight of styrene units and the balance of butadiene units; said styrene units having at least 40% by weight of the single isolated styrene units which are separated from each other and 5% by weight or less of the styrene units in the form of long chain blocks each consisting of 8 or more styrene units bound to each other, based on the entire weight of said styrene units in the copolymer; said butadiene units having 35% to 50% by mole of butadiene units in the form of 1,2-vinyl structure based on the entire mole of said butadiene units in the copolymer; said styrene-butadiene copolymer rubber having the ratio (Mw/Mn) of 1.2 to 3.5, wherein Mw and Mn represent the weight average and number average molecular weights, respectively; and said styrene-butadiene copolymer rubber having a coupling efficiency of 40% or more; and said carbon black being a furnace carbon black having (1) a specific surface area (N 2 SA) in the range of 75 to 105 as measured by nitrogen adsorption technique, (2) the difference between said N 2 SA value and the measured iodine adsorption value (IA) being at least 15 (i.e., N 2 SA-IA≧15) and (3) the difference between said N 2 SA value and the measured specific surface area (CTAB) as determined by the cetyltrimethylammonium bromide adsorption technique being not greater than 5 (i.e., N 2 SA-CTAB≦5); said furnace carbon black also having a dibutyl phthalate adsorption value (24M4 DBP) of not greater than 110 (ml/100 g) and a tinting strength (Tint) of 90 to 110, provided that the difference (ΔTint) between the measured Tint and the calculated Tint of the furnace carbon black is not greater than -3 [i.e., (measured Tint)-(calculated Tint)≦-3].

What is claimed is: 
     
       1. A rubber tire composition, comprising: from 20-150 parts by weight of carbon black incorporated in 100 parts by weight of rubber; said rubber comprising at least 30 parts by weight of a star type solution polymerized, random styrene-butadiene copolymer rubber and no more than 70 parts by weight of at least one other diene rubber, said random styrene-butadiene copolymer rubber comprising 10% to 20% by weight of styrene units and the balance of butadiene units; said styrene units having at least 40% by weight of the single isolated styrene units which are separated from each other and 5% by weight or less of the styrene units in the form of long chain blocks each consisting of 8 or more styrene units bound to each other, based on the entire weight of said styrene units in the copolymer; said butadiene units having 35% to 50% by mole of butadiene units in the form of 1,2-vinyl structure based on the entire mole of said butadiene units in the copolymer; said styrene-butadiene copolymer rubber having the ratio (Mw/Mn) of 1.2 to 3.5, wherein Mw and Mn represent the weight average and number average molecular weights, respectively; and said styrene-butadiene copolymer rubber having a coupling efficiency of 40% or more; and said carbon black being a furnace carbon black having (1) a specific surface area (N 2  SA) in the range of 75 to 105 as measured by nitrogen adsorption technique, (2) the difference between said N 2  SA value and the measured iodine adsorption value (IA) being at least 15, as represented by the formula N 2  SA-IA≧15, and (3) the difference between said N 2  SA value and the measured specific surface area (CTAB) as determined by the cetyltrimethylammonium bromide adsorption technique being not greater than 5, as represented by the formula N 2  SA-CTAB≦5; said furnace carbon black also having a dibutyl phthalate adsorption value (24M4 DBP) of not greater than 110 (ml/100 g) and a tinting strength (Tint) of 90 to 110, provided that the difference (Δ Tint) between the measured Tint and the calculated Tint of the furnace carbon black is not greater than -3, as represented by the formula (measured Tint)-(calculated Tint)≦-3.   
     
     
       2. The composition of claim 1, wherein said star type solution polymerized styrene-butadiene copolymer rubber is coupled with tin tetrachloride. 
     
     
       3. The composition of claim 1, which further comprises at least one additive selected from the group consisting of a vulcanizing agent, a vulcanization acceleration aid, a vulcanization accelerator, an anti-oxidant, a softening agent and a filler. 
     
     
       4. The composition of claim 1, wherein said composition further contains 70 parts by weight or less of other diene rubber.